Widely accepted are two notions: sleep deprivation impairs health and sleep recovery has dynamic healing powers. The rationale for the proposed research is that specific tissues have not yet been identified as being in need of repair after sleep deprivation or "restored" by sleep recovery. Our long-term goal is to provide tangible evidence of physiological processes and outcomes that compose the properties of sleep and sleep loss. Sleep deprivation in the animal model produces a condition that eventually becomes highly lethal, lacks specific localization, and is reversible with sleep, implying mediation by a biochemical process or functional abnormality. Recent findings in sleep-deprived rats have provided evidence that the missing biological mediation is oxidative stress and antioxidant depletion. The objectives of this proposal are to identify targets of oxidative stress-associated damage and to determine the extent to which antioxidant depletion and cell damage affect physiological and clinical signs. The central hypothesis is that reductions in antioxidant status cause widespread increases in repairable and irreparable cell damage within multiple regulatory systems, leading ultimately to inadequate compensation and to the development of pathophysiological signs. Preliminary data support the formulation of this hypothesis by providing evidence of increased DNA damage and apoptosis in hepatic tissue undergoing oxidative stress induced by sleep loss. Antioxidant enzymes fail to respond in compensation until sleep is again permitted. In experiments under Aim 1, damage to cellular lipid, protein, and DNA targets of oxidative stress and localization of damage to specific organ-systems will be determined in rats during sleep loss and recovery. Experiments under Aim 2 will determine the extent of cell injury leading to cell death and to increased cell repair and renewal during sleep loss and recovery. Studies under Aim 3 will test the extent to which manipulation of antioxidant status can change sleep deprivation-induced cell damage and physiological signs. The proposed research is collaborative and integrates expertise in sleep physiology and free radical biology. The research design is composed of planned comparisons of different durations of sleep deprivation, sleep restriction, and control conditions. Analyses include biochemical, immunoassay, and immunohistochemical methods. The significance of the proposed research is advancement of medical interventions that promote the restorative functions of sleep.